The objectives of this placebo-controlled, randomized, blinded study are to evaluate the safety and efficacy of intravenous administration of the neuraminidase inhibitor zanamivir (GG167) in experimentally induced influenza A (H1N1) infection in healthy male volunteers. Sero- susceptibles will be given zanamivir 600 mg or placebo by IV infusion every 12 hours for 5 days, inoculated intranasally with influenza virus 4 hours after the first dose, and then monitored for 7 days as inpatients by standard methods. Study is completed. Analysis of samples is in progress.